Effectiveness and safety of aldosterone antagonist therapy use among older patients with reduced ejection fraction after acute myocardial infarction

Background-While aldosterone antagonists have proven benefit among post-myocardial infarction (MI) patients with low ejection fraction (EF), how this treatment is used among older MI patients in routine practice is not well described. Methods and Results-Using ACTION Registry-GWTG linked to Medicare data, we examined 12 080 MI patients ≥65 years with EF ≤40% who were indicated for aldosterone antagonist therapy per current guidelines and without documented contraindications. Of these, 11% (n=1310) were prescribed aldosterone antagonists at discharge. Notably, 10% of patients prescribed an aldosterone antagonist were eligible for, but not concurrently treated with, an angiotensin-converting enzyme inhibitor/angiotensin receptor blocker. Spironolactone was the predominantly prescribed aldosterone antagonist. At 2-year follow-up, aldosterone antagonist use was not associated with lower mortality (unadjusted 39% versus 38%; HR 0.99, 95% CI 0.88-1.33 using inverse probabilityweighted propensity adjustment) except in symptomatic HF patients (HR 0.84, 95% CI 0.72-0.99, P_interaction=0.009). Risks of hyperkalemia were low at 30 days, but significantly higher among patients prescribed aldosterone antagonists (unadjusted 2.3% versus 1.5%; adjusted HR 2.04, 95% CI 1.16-3.60), as was 2-year risk of acute renal failure (unadjusted 6.7% versus 4.8%; adjusted HR 1.39, 95% CI 1.01-1.92) compared with patients not prescribed aldosterone antagonists. Conclusions-Aldosterone antagonist use among eligible older MI patients in routine clinical practice was not associated with lower mortality except in patients with HF symptoms, but was associated with increased risks of hyperkalemia and acute renal failure. These results underscore the importance of close post-discharge monitoring of this patient population.